U.S. Pat. No. 4,615,338 (incorporated by reference herein) to Ilizarov discloses an orthopaedic procedure employing an external device which fixes to the bone by means of slender pins and which tensions or distracts the bone at a doctor-selected rate and rhythm of tensioning or distraction, with resulting growth of new bone, skin, muscle and nerves. The Ilizarov external fixation system uses a variety of perforated rings connected by graduated telescopic rods. Generally, the rods are distracted 1/4 of a millimeter four times a day for a total distraction of 1 mm per day. When the desired length is achieved, the bone is then held in place to allow consolidation. The consolidation period is generally the same as the time needed for distraction, generally. Thus, for a distraction period of four weeks, the consolidation period would be four weeks, for a total treatment time of eight weeks. Research shows that a rate of distraction of 1/60 of a mm sixty times a day produces even better results than 1/4 of a mm increments.
Generally, in the Ilizarov system, the nuts of the graduated telescopic rods interconnecting the support members are turned manually to cause distraction. U.S. Pat. No. 4,615,338 discloses an automatic drive system employing a lead screw mated with a ratchet wheel placed in a housing, and a pawl interacting with teeth of the ratchet wheel to drive the ratchet wheel to adjust the length of the telescopic rod.